This invention relates generally to improvements in methods and apparatus for effecting an electrotherapeutic treatment on a biological subject, such as iontophoretic delivery of medicaments and, more particularly, to a new and improved system for the application of an iontophoretic treatment topically to the skin of a human body.
Around the turn of the century there was disclosed a plethora of electrode types for applying "electric treatments" to the human body. The electrodes were normally placed upon the body in relation to the position of the organ to be treated. Such "electric treatments" encompassed a wide range of applications. For example, galvanic (direct current) treatments have been popular in the past for their polar effects on ionized molecules, causing the ionized molecules to be driven through the skin, usually superficially. This phenomenon is known as iontophoresis or ion transfer, and it has been employed for the introduction of medicaments or even simply moisture, into the skin of a patient.
More specifically, and by way of example, some ions of zinc and copper can be employed in the treatment of various skin infections, and chlorine ions have been employed for the loosening of superficial scars. Further, vasodilating drugs can be used in rheumatic and peripheral vascular affections, and skin anesthesia can be produced by iontophoresis of local anesthetic drugs. Moreover, iontophoretic administration of drugs typically avoids the gastrointestinal side effects sometimes associated with direct ingestion of such drugs.
Although the aforementioned iontophoretic treatments have been found to be effective, they are also known to be accompanied by a number of undesirable side effects, such as the occurrence of skin injury in the form of iontophoretic burns and irritation in the treated area, as well as the formation of undesirable vesicles and bulla, on the skin in the treated area. Various complicated or compromised methods for preventing these iontophoretic burns have been developed. However, such methods and apparatus have generally been found not to be adequately effective for preventing irritation and the formation of vesicles or bulla on the skin in the treated area. Consequently, iontophoretic treatments have usually been limited to relatively low electrical currents and relatively short periods of administration of, typically, twenty minutes or less.
Iontophoretic drug delivery systems of the prior art have also been primarily limited to delivering a drug of only a single polarity at a time to a given area, at relatively low concentrations, and have not been suitable for simultaneous delivery of multiple drugs. Furthermore, there were virtually no satisfactory iontophoretic devices which were relatively simple, economical, compact, portable and capable of safe, long term delivery over several days, once applied to the patient and placed into operation. Attempts to meet these needs have involved rather complex buffering, electrical or other compensatory systems which have not proven entirely practical or satisfactory.
In addition to the foregoing difficulties, iontophoretic systems of the past have not proven effective in the administration of drugs embodying relatively large and/or heavy molecular structures. Moreover, drug formulations intended for iontophoretic therapeutic drug delivery have oftentimes required buffering agents for pH control. Control of pH at the delivery site of the therapeutic drug has been essentially unknown. Furthermore, difficulties in obtaining sufficiently high rates of infusion, due to relatively high electrical resistance and/or poor permeability at the delivery site, have also been encountered with iontophoretic systems.
The aforementioned difficulties and undesirable side effects of iontophoretic treatment have resulted in a sometimes less than enthusiastic reception of iontophoretic techniques by the medical community, in spite of the potentially great and varied advantages to be realized through their use and development.
Hence, those concerned with development and use of iontophoretic systems in the medical field have long recognized the need for a convenient and effective apparatus and method for preventing burns, irritation and the formation of vesicles and bulla on the skin in an area subjected to an iontophoretic treatment over extended periods of continuous treatment, for systems which can be physically packaged in a relatively simple, economical and compact configuration, can deliver therapeutic drugs at a relatively high rate and at higher concentrations, without the need for buffering agents and the like, which are capable of delivering large molecular substances such as insulin and the like, can deliver a plurality of drugs simultaneously in a relatively simple manner without matching drug polarity, can be used to lower resistance and increase permeability, and can be used to reliably control pH at the drug administration site. As will become apparent from the ensuing discussion, the present invention clearly fulfills all of these needs and more.